Art - you might try scanning B&W negs as positives, and then invert in your photo editor. I'm not sure which software came with your Canon, but I sometimes need to do that with the Epson and Silverfast.

It's worth a shot! Otherwise I have no idea what to do about it. The Canon editing software that came with the scanner is poor and is primarily concerned with e-mailing your snaps to Grandma. The actual scanning software is 'Scan Gear CS' and it's very basic. Fortunately they also bundled PhotoShop Elements 2.0 with it and that's what I use for editing.